The transformation of light energy into electrical energy using photovoltaic (PV) systems has been known for a long time and such photovoltaic energy conversion systems are increasingly being implemented in residential, commercial, and industrial applications. Rapid detection of unintended shunting of DC current to ground, also known as a ground fault, is mandatory for implementation of such systems because ground faults present potentially dangerous conditions, including fire risk. Accordingly, for safety reasons photovoltaic energy conversion systems must rapidly detect ground fault conditions and automatically interrupt operation when appropriate.
Photovoltaic systems typically include, among other components, a photovoltaic array that generates DC power and an inverter that converts the DC power to AC power (e.g., single phase or three phase power). In such systems, a ground fault detector and interrupter (GFDI) is typically employed to detect DC current flowing between the PV array and ground. Some of the components used in a ground fault detector and interrupter are not capable of being certified as high integrity components, which means that the reliability of such components as used in the ground fault detector and interrupter is not guaranteed to be at an acceptable level. Because the ground fault detector and interrupter is often critical to the safe operation of the PV energy conversion system, measures must be taken to ensure that the ground fault detector and interrupter operates correctly at all times. Accordingly, apparatus and methods are needed to ensure continuously that the ground fault detector and interrupter is operating correctly.